Linear actuator and method of manufacturing linear actuator including a deaerating step

Abstract

A linear actuator includes a linear actuator body ( 2 ), a casing ( 3 ) for housing the linear actuator body ( 2 ), and insulating oil (L) that fills the casing ( 3 ) with a coil ( 44 ) of the linear actuator body ( 2 ) submerged therein. In such a configuration, heat generated by the coil ( 44 ) is quickly released to the oil (L) and is then conducted to the casing ( 3 ). The oil (L) fully spreads into gaps in the coil ( 44 ), of course. Therefore, heat is released very efficiently. Thus, by improving the heat-releasing characteristic, a linear actuator having a reduced size and a reduced weight is provided.

What is claimed is: 
     
       1. A linear actuator comprising:
 a linear actuator body including a stator having a leaf spring that supports a mover so as to be reciprocatable, the mover being reciprocatable in a specific direction relative to the stator and a coil that causes the mover to reciprocate; 
 a casing substantially enclosing the linear actuator body with a part of the linear actuator body secured thereto; and 
 a liquid that fills an internal space of the casing with the coil and the leaf spring of the linear actuator body submerged in the liquid, the liquid being lubricating and electrically insulating, 
 wherein the liquid is deaerated prior to or after the internal space is filled with the liquid. 
 
     
     
       2. The linear actuator according to  claim 1 , wherein a part of the stator is secured to the casing, a part of the casing is secured to an object which is subject to a vibration control, whereby a reaction force produced by reciprocating the mover is transmitted to the object through the stator and the casing. 
     
     
       3. The linear actuator according to  claim 1 , wherein bubbles are not present between the linear actuator body and the liquid. 
     
     
       4. The linear actuator according to  claim 1 , further comprising:
 a gas-permeable material provided on the casing such that a gas in the internal space of the casing can permeate to outside of the casing. 
 
     
     
       5. A method of manufacturing a linear actuator, the method comprising:
 a step of housing a linear actuator body in a casing, the linear actuator body including a stator having a movable supporting portion that supports a mover so as to be reciprocatable, the mover being reciprocatable in a direction relative to the stator, a coil that causes the mover to reciprocate, and a casing substantially enclosing the linear actuator body with a part of the linear actuator body secured thereto; 
 a step of filling an internal space of the casing with a liquid that is lubricating and electrically insulating, with the coil and the movable supporting portion being submerged in the liquid; and 
 a step of preventing formation of bubbles between the movable supporting portion and the liquid, 
 wherein the step of preventing formation of bubbles between the movable supporting portion and the liquid comprises a step of deaerating the liquid before the completion of the step of filling. 
 
     
     
       6. The method according to  claim 5 , wherein the step of preventing formation of bubbles between the movable supporting portion and the liquid comprises a step of removing the bubbles, formed between the liquid having been supplied in the step of filling, and the linear actuator body. 
     
     
       7. The method according to  claim 6 , wherein the step of preventing formation of bubbles between the movable supporting portion and the liquid further comprises a step of causing the mover to reciprocate. 
     
     
       8. The method according to  claim 7 , wherein the step of preventing formation of bubbles between the movable supporting portion and the liquid further comprises a step of vibrating the casing and the liquid therein. 
     
     
       9. The method according to  claim 8 , wherein the casing is vibrated with a frequency higher than that of reciprocation of the mover. 
     
     
       10. The method according to  claim 6 , wherein the linear actuator includes a gas-permeable material provided on the casing such that a gas in the internal space of the casing can permeate to outside of the casing, and wherein the step of preventing formation of bubbles between the movable supporting portion and the liquid further includes a step of deaerating the liquid through the gas-permeable material. 
     
     
       11. The linear actuator according to  claim 1 , wherein bubbles are not present between the leaf spring and the liquid. 
     
     
       12. The linear actuator according to  claim 1 , wherein the liquid is deaerated prior to the internal space being filled with the liquid. 
     
     
       13. The linear actuator according to  claim 12 , wherein the liquid is supplied to the casing to allow the liquid to run along an inner wall of the casing. 
     
     
       14. The linear actuator according to  claim 12 , wherein the liquid fills 80% to 95% of the internal space. 
     
     
       15. The linear actuator according to  claim 1 , wherein the liquid is deaerated after the internal space is filled with the liquid. 
     
     
       16. The linear actuator according to  claim 15 , wherein the liquid is deaerated by shaking the casing. 
     
     
       17. The linear actuator according to  claim 16 , wherein the liquid fills 80% to 95% of the internal space.